From MATH REVIEWS (for the German edition): "The book is addressed to students of mathematics at the undergraduate or first year graduate level, with the objective of critically examining and clarifying the assumptions underlying basic concepts and axioms. For this purpose, the examples for the continuum, geometry and the theory of computability are used. The goal of getting the nonspecialist interested in foundational problems, and awakening a critical level of appreciation, is achieved to perfection by this text via a well thought out, successful selection both of the topics and of the level of analysis devoted to the individual themes."